1. Field of Invention
The present invention relates to a resonator, a manufacturing method of the resonator, and a signal processing method using the resonator. More particularly, the present invention relates to an MEMS (Micro-Electro Mechanical System) resonator, a manufacturing method of the MEMS resonator, and a signal processing method using the MEMS resonator in the field of wireless communication and sensor applications.
2. Description of Related Art
A Micro-Electro Mechanical System, or MEMS, is formed by an industrial technology using micro- or nano-matching techniques combined with micro-electronics. The MEMS is more miniaturized, and has the properties of relatively high accuracy, low cost and can be mass-produced as compared with a conventional electro mechanical system. The MEMS can be applied to various fields, such as biology, medicine, chemistry, optics, thermal physics, electronics, semiconductors technologies, etc. Thus, the conventional electro mechanical system has been gradually replaced by the MEMS. Applications and performance of the MEMS depend on its manufacturing material, manufacturing approach, and structure.
As compared with a conventional transistor circuit, a MEMS electric component such as a resonator, an oscillator, a clock generator, a filter, and a mixer has a relatively high-quality factor, low power loss, high feasibility in the field of wireless communication and sensor applications, and can be combined with existing IC manufacturing skills. Therefore, the MEMS technique has a much higher quality-price ratio than a conventional mechanical manufacturing skill. Besides, the integration of the MEMS technique can be more diversified through programmable functions, and thus the MEMS technique is vigorously grown in a wireless communication field, especially in an RF (Radio Frequency) field.
In the past, in order to obtain high-quality factor performance, passive components cannot be shrunk and integrated with transistor circuits. Furthermore, the bulky size and exotic nature of the entire RF system demands a discrete feature, and the discrete feature further impedes system miniaturization, integration, and thus impedes cost reduction of future portable electronics.
Generally, resonators can be classified into four types according their transduction mechanisms, which are piezoelectric, electrostatic, electromagnetic, and magnetostrictive types. U.S. Pat. No. 7,023,065 discloses an electrostatic MEMS resonator (i.e. a capacitive resonator) and a manufacturing method thereof. The capacitive resonator is configured as a in-plane clamped-clamped beam resonator formed from single crystal silicon. An electronic signal is applied to a driving electrode to induce an electrostatic field on the in-plane clamped-clamped beam resonator, and the electrostatic field enables the oscillator to create an oscillation signal. When the frequency of the oscillation signal is equal or close to that of the electronic signal, a change of the gap between the drive electrode and the clamped-clamped beam is generated. The oscillation signal can further be measured by a sensing electrode which senses an electronic signal converted from the change.
A piezoresistive MEMS resonator and a manufacturing method thereof have been disclosed in CN Patent Application No. 201010604008. The piezoresistive MEMS resonator includes an anchor, a resonator arranged on the anchor, an electrostatic force which has been created from an actuator applied to the resonator, and a device for reading out piezoresistive values comprises a nanowire coupled to the resonator, wherein the resonator includes an area of at least 100 μm2, and the nanowire includes a cross-section area of at most 10−14 m2. A giant piezoresistive effect is shown while a low power miniature piezoresistive readout scheme is combined with a bulk resonator. Since the giant piezoresistive effect created in a silicon nanowire is much larger than the piezoresistive effect created in a bulk resonator, the signaling speed thereof can be enhanced
U.S. Pat. No. 7,750,759 discloses a multi-mode MEMS resonator system including electrostatic resonators and piezoelectric resonators. Different materials are chosen to be used with the identical structure to achieve a purpose of substituting the electrostatic type with the piezoresistive type or the piezoresistive type with the electrostatic type while in use.